Clay
served for centuries as an affordable and reliable material from which to make
containers. Clay is a mineral whose particles are flat and plate-like. With
just the right amount of water content, this shape allows the particles to
slide over each other without breaking apart.

A pot that has simply been dried will break apart and become a shapeless mass
again if it gets wet. But, when fired—heated at very high temperatures
such as in a bonfire or kiln—the clay is transformed into a rock-like
material. Fired pots are porous, which means air and water can pass
through the walls of the pot but it will still retain its shape. However,
applying a glaze—a thin coating of clay and pigment—to the pot before
firing will make it watertight.